This invention relates to temperature indicating apparatus and more particularly to portable probe-type electronic thermometers for clinical measurement of body temperature.
Such electronic thermometers have increasingly been used in hospitals and clinics, etc. These thermometers, which display the temperature being measured either by a digital indication or by an analog indication such as the position of a pointer on the face of a meter, have many advantages over glass-bulb thermometers which have a slow response, are difficult to effectively sterilize and have a high rate of breakage.
The existing electronic thermometers, however, are not without disadvantages. Some digital and analog readout electronic thermometers, for example, display a series of increasing preliminary temperature readings prior to displaying an accurate temperature of the zone being measured and this can mislead an incautious user into believing an erroneous preliminary temperature reading is the final correct reading.
The types of readouts typically employed with current instruments provide temperature displays which do not permit users to utilize interpretive or judgmental factors in evaluating the temperature data provided. Thus, in thermometers having digital displays the user is usually provided with a three or four digit readout which is the only information that can be read and recorded. If the display is partially inoperative, for example if one segment of a sevensegment light emitting diode display is not functioning, the temperature display may be incorrect, but the user has no way of determining this. Similarly, if the display is obscured as by dirt or fingerprints, etc. on the display cover, the user again may misread the temperature and have no way of knowing that she has done so. It is also possible for the user to simply misread the temperature indicated especially under the extremely busy conditions which are not uncommon in hospitals. In each of these situations, the reading may easily be more than 1.degree. in error and thus significant. Further, small changes may occur in the instrument from one measurement to the next resulting in a digital display that differs from one reading to another even though a person's temperature is unchanged. Because the users can read only the temperature displayed, there is no way they can use their experience and other judgmental factors to interpret what is provided by the instrument. Digital type thermometers also provide a display that is either in .degree. F. or .degree. C. but not in both. If the temperature is read in one scale but needs to be recorded in the other, a temperature conversion is required which both consumes time and leads to error.
Electronic thermometers having analog displays do not have the last-mentioned disadvantage of digital display instruments. However, analog display instruments typically use a meter with a pointer and bearings therefor and thus are particularly susceptible to damage resulting from mechanical shock, as occurs if an instrument is dropped or otherwise mishandled, and from wear. This is also true of mechanical type digital display thermometers. Again, reading errors may occur because of misreading of the display either because of damage to the instrument, obscuring of the display or human error.
Other disadvantages with present electronic thermometers include general susceptibility to damage when dropped or otherwise mishandled. In such cases, the thermometer may become either partially or wholly inoperable and the accuracy of the readout becomes unreliable or questionable.
Some of the prior electronic thermometers have a provision for displaying a series of sequential digits to establish a given time period, e.g., 20 second during the time between the introduction of the probe into the region and the time the correct temperature thereof can first be accurately displayed. While this is a useful feature, the user counting the patient's pulse beats can be confused by the series of digits displayed at one second increments which can lead to reporting an erroneous pulse. Additionally, the temperature display of many existing electronic thermometers cannot be read under adverse conditions as, for example, when a patient is kept in a darkened room. Also, there are problems of pilferage, particularly where the instrument is "pocket sized", and the batteries of existing electronic thermometers must be frequently replaced generally because they are subject to a high battery drain when in use.
Representative patents which are of interest in the same general field as that of the present invention, include U.S. Pat. Nos. 3,702,076, 3,822,598 and 3,906,797.